JP5034784B2 - Method for dehydrating hexafluroacetone hydrate - Google Patents

Description

  The present invention relates to a method for dehydrating hexafluoroacetone hydrate with hydrogen fluoride, and also relates to a method for producing a hexafluoroacetone hydrogen fluoride adduct.

  Hexafluoroacetone is produced in large quantities as industrial raw materials such as 2,2-bis (4-hydroxyphenyl) hexafluoropropane (bisphenol-AF), which is important as a cross-linking agent for fluororubber, and hexafluoroisopropanol, which is important as a pharmaceutical intermediate. Has been. Hexafluoroacetone is industrially produced by epoxidation of hexafluoropropene followed by isomerization, hexachloroacetone obtained by chlorinating acetone with hydrogen fluoride using a chromium activated carbon supported catalyst, etc. Manufactured. Hexafluoroacetone is a gas having a boiling point of −28 ° C. at atmospheric pressure. For convenience in handling, hexafluoroacetone trihydrate obtained as a constant boiling point composition at 106 ° C. is a raw material in many reactions. Or used for storage. However, the presence of water may not be allowed depending on the reaction conditions, target product and other requirements, and hydrates are usually less reactive than anhydrides. Is often required, and in use, the hydrate is often converted to the anhydride in situ.

  As a method for dehydrating hexafluoroacetone hydrate, a method involving contact with molecular sieve (registered trademark) (Patent Document 1), concentrated sulfuric acid, anhydrous sulfuric acid, phosphorus pentoxide (Patent Document 2), or the like has been reported. When concentrated sulfuric acid, anhydrous sulfuric acid, phosphorus pentoxide, fuming sulfuric acid, etc. are used as dehydrating agents, hexafluoroacetone decomposition products may be generated, and a large amount of sulfuric acid and phosphoric acid containing water and decomposition product organic substances may be produced. Waste is generated. Further, there is a problem that the recovery rate of hexafluoroacetone is not necessarily high when dehydration is performed by these methods including the case of using synthetic zeolite.

On the other hand, in a reaction using hexafluoroacetone as a raw material, hydrogen fluoride may be used as a catalyst or a solvent. For example, bisphenol-AF is obtained by a dehydration reaction from a mixture of hexafluoroacetone, phenol, and hydrogen fluoride (Non-patent Document 1).
JP 59-157045 A JP-A-57-81433 Isz. Akad-Nauk SSSR, Otdel. Khim, Nauk, vol.4 pp.686-692 (1960); English version pp.647-653

    A method for dehydrating hexafluoroacetone hydrate to obtain a mixture of hexafluoroacetone hydrogen fluoride adduct and hydrogen fluoride, which does not substantially generate waste is provided.

  The present inventors examined a method for industrially producing a hexafluoroacetone hydrofluoride adduct exhibiting the same reaction behavior as hexafluoroacetone in a specific reaction. As a result, hexafluoroacetone hydrate was converted to hydrogen fluoride. Hydrogen fluoride of hexafluoroacetone hydrofluoride adduct is obtained by dehydrating hexafluoroacetone hydrate with high yield by a simple method consisting of mixing and distilling with substantially no waste generation The inventors have found that the solution can be produced quantitatively and have completed the present invention.

That is, the present invention is made by bringing hexafluoroacetone hydrate into contact with hydrogen fluoride and distilling it as it is, from a component comprising hexafluoroacetone hydrogen fluoride adduct and hydrogen fluoride, water and hydrogen fluoride. It is a manufacturing method of the hexafluoroacetone hydrogen fluoride adduct which consists of dividing | segmenting into each component and obtaining.
[Claim 1] Hexafluoroacetone hydrate and hydrogen fluoride are mixed in advance or separately introduced into a distillation column, and hexafluoroacetone or hexafluoroacetone hydrogen fluoride adduct and hydrogen fluoride are introduced as a low boiling point component. A method for dehydrating hexafluoroacetone hydrate comprising obtaining a composition comprising water and obtaining a composition containing water and hydrogen fluoride as high-boiling components.
[Claim 2] The dehydration method according to claim 1, wherein hexafluoroacetone hydrate and hydrogen fluoride are mixed in advance or separately separately introduced into the distillation column.
[Claim 3] Hexafluoroacetone hydrate and hydrogen fluoride are mixed in advance or separately introduced continuously into a distillation column, and hexafluoroacetone or hexafluoroacetone hydrofluoride adduct and fluorine are added as low boiling point components. A method for dehydrating hexafluoroacetone hydrate comprising continuously obtaining a composition containing hydrogen fluoride from the top of the column and continuously obtaining a composition containing water and hydrogen fluoride as high-boiling components from the bottom of the column.
[4] The dehydration method according to any one of [1] to [3], wherein the hexafluoroacetone hydrate is hexafluoroacetone trihydrate.
[5] The dehydration method according to any one of [1] to [4], wherein the hexafluoroacetone hydrate is hexafluoroacetone hydrate containing water.

  In the dehydration method of the present invention, since the obtained hexafluoroacetone or hexafluoroacetone hydrogen fluoride adduct is a mixture with hydrogen fluoride, the reaction using hexafluoroacetone as a raw material, catalyst or solvent is used. Is effective in simplifying the process because it can be used as it is, and also requires waste treatment such as waste sulfuric acid containing organic substances that cannot be avoided by the conventional methods using concentrated sulfuric acid, fuming sulfuric acid, etc. This is an excellent method in terms of environmental protection.

Hereinafter, the present invention will be described in detail.
In the specification, hydrogen fluoride may be expressed as “HF”.
In the specification, hexafluoroacetone may be represented as “HFA”.
In the specification, the hexafluoroacetone hydrogen fluoride adduct may be expressed as “HFA · HF”.
In the specification, hexafluoroacetone hydrate refers to a hydrate that does not limit the number of hydration or an aqueous solution thereof, and includes hexafluoroacetone trihydrate.
In the specification, hexafluoroacetone trihydrate may be represented as “HFA · 3W”.

  In the present invention, hexafluoroacetone hydrate is brought into contact with hydrogen fluoride and distilled as it is, so that a component composed of hexafluoroacetone hydrogen fluoride adduct and hydrogen fluoride, and a component composed of water and hydrogen fluoride. It is a manufacturing method of the hexafluoroacetone hydrogen fluoride adduct which consists of respectively dividing | segmenting and obtaining. Here, “as is” means that treatment with an adsorbent such as a chemical substance or molecular sieve generally used as a “dehydrating agent” such as concentrated sulfuric acid, sulfuric anhydride, or phosphorus pentoxide is not performed. .

  HFA-3W, which is sometimes handled as an alternative reaction reagent for hexafluoroacetone,

As described above, it is a dihydrate of gem-diol obtained by reacting hexafluoroacetone and water, and is a liquid having a boiling point of 106 ° C. Even if HFA · 3W is distilled, water cannot be released to obtain hexafluoroacetone.

  Hexafluoroacetone monohydrate is a compound different from hexafluoroacetone and is expressed as gem-diol. The equilibrium of the following formula is established between hexafluoroacetone and water, and the equilibrium is remarkably to the right. I'm offset.

Hexafluoroacetone monohydrate is a highly sublimable, highly hygroscopic solid with a melting point of 52 ° C. and decomposes at 46 ° C. However, like HFA · 3W, hexafluoroacetone cannot be obtained by distillation.

  On the other hand, the hexafluoroacetone hydrogen fluoride adduct is a 1: 1 adduct of hexafluoroacetone and hydrogen fluoride represented by the following formula: heptafluoroisopropanol. Heptafluoroisopropanol is a thermally unstable compound by itself, and at temperatures above the boiling point (14 to 16 ° C.), it is partially decomposed into hexafluoroacetone and hydrogen fluoride, and the equilibrium of the following formula holds: It is done. The equilibrium depends on the temperature, with 35% heptafluoroisopropanol being decomposed at 20 ° C. and 70% at 100 ° C.

Although it has been reported that HFA / HF can be separated by distillation in a non-equilibrium state (US Pat. No. 3,745,093), it is not possible to separate hexafluoroacetone and hydrogen fluoride by distillation by an ordinary method. (French Patent No. 1372549).

  In the process of completing the present invention, by the inventors, HFA · HF is heptafluoroisopropanol, and when excessive amount of hydrogen fluoride coexists, it should exist stably as heptafluoroisopropanol without decomposition even at room temperature or higher. Was confirmed by NMR measurement in hydrogen fluoride.

  The dehydration of the hexafluoroacetone hydrate of the present invention can be carried out by using a general distillation apparatus equipped with a distillation can, a distillation column, a condenser and other apparatuses, and is either batch type, semi-batch type or continuous type. It can also be implemented in the form. As the material of the apparatus, stainless steel, nickel alloy steel, silver, fluororesin, carbon, polyethylene, or a metal material lined or clad with these materials can be used. For distillation cans and distillation columns and fillers that come into contact with a relatively high temperature hydrogen fluoride aqueous solution, it is preferable to use a resin material that can withstand a hydrogen fluoride aqueous solution such as silver or fluororesin, or a metal material that is lined or clad with these materials. . The distillation column can be either a packed type made of a known packing material or a plate tower.

  Although the method of the present invention can be carried out under reduced pressure or under pressurized conditions, specifically, under a pressure condition of about 0.05 to 2 MPa, a case where it is carried out under atmospheric pressure will be described below. Performing under other pressure conditions is also within the scope of the present invention, and it is easy for those skilled in the art to optimize the conditions based on the following description and common general technical knowledge in this technical field.

  The batch type dehydration method will be described.

  HFA · 3W and hydrogen fluoride are introduced into a distillation can (column bottom) of the distillation column. Although 1 mol or more of hydrogen fluoride is required with respect to 1 mol of HFA · 3W, 2 to 100 mol is preferable, 3 to 50 mol is more preferable, and 5 to 30 is more preferable. If the amount of hydrogen fluoride is too small, the effect of dehydration will be insufficient, and the operation of distillation will not be stable. If it is excessive, there will be no problem in the effect of dehydration, but the consumption of utilities will increase and the equipment will become larger Each is not preferable. Here, HFA · 3W may be hexafluoroacetone hydrate, may have a hydration number of less than 3, such as hexafluoroacetone monohydrate, and hexafluoroacetone hydrate. The raw material used for dehydration is preferably HFA · 3W or a material having a smaller hydration number than that. Anhydrous hydrogen fluoride available for industrial use is suitable as the hydrogen fluoride, but one containing about 50% by mass of water can also be used.

  When the column bottom temperature is increased to exceed the boiling point of hydrogen fluoride, the vapor is liquefied by the condenser at the top of the column and starts to reflux, and after a certain time, approaches the boiling point of 16 ° C. of HFA / HF. When the reflux liquid is gradually withdrawn, the temperature approaches the boiling point of hydrogen fluoride (19.5 ° C.), but the reflux liquid is withdrawn while adjusting to maintain the reflux state. When the reflux amount decreases, the column bottom temperature is gradually increased. At the beginning of distillation, a component containing a large amount of HFA / HF is withdrawn from the top of the column at 16 to 20 ° C., and then the temperature of the reflux liquid gradually rises and the content of HFA / HF decreases to contain a large amount of hydrogen fluoride. Although the components are extracted, the temperature of the reflux liquid must be maintained within a range that does not greatly exceed the boiling point of hydrogen fluoride. Otherwise, the dehydration of hydrogen fluoride will be incomplete and water will be contained in the column top liquid. Further distillation is continued, and the temperature at the bottom of the column determined by the composition of hydrogen fluoride and water can be continued until the azeotropic temperature of the aqueous hydrogen fluoride solution rises to 112 ° C. At this time, the bottom liquid of the column forms the highest azeotropic composition of 62% by mass of hydrogen fluoride and 38% by mass of water. The column bottom liquid is substantially free of hexafluoroacetone. The tower bottom temperature can be up to the maximum azeotropic temperature of the aqueous hydrogen fluoride solution, and can be lower than the maximum azeotropic temperature as long as it is higher than the boiling point of hydrogen fluoride (19.5 ° C.). In this case, a hydrogen fluoride aqueous solution having a concentration determined by the boiling point is obtained, but the concentration may be determined depending on the use of the hydrogen fluoride aqueous solution. In this way, a component composed of hexafluoroacetone or HFA.HF and hydrogen fluoride and a component composed of hydrogen fluoride and water (hydrogen fluoride aqueous solution) are obtained separately.

  Next, the case where the method of this invention is performed by a continuous method is demonstrated.

  In the batch dehydration method described above, it is preferable to shift from a state in which the distillation column is maintained in a stable reflux state to a continuous method. In the continuous method, it is easy to use hexafluoroacetone hydrate having a constant composition ratio of hexafluoroacetone and water, for example, HFA · 3W. HFA · 3W and hydrogen fluoride are continuously introduced into the distillation column, HFA · HF and hydrogen fluoride are continuously withdrawn from the top of the column, and an aqueous hydrogen fluoride solution is continuously withdrawn from the bottom of the column. Continuous operation of introduction of hexafluoroacetone hydrate and hydrogen fluoride, extraction of HFA / HF and hydrogen fluoride from the top of the column, and extraction of aqueous hydrogen fluoride solution from the bottom of the column can be performed intermittently. .

  Hexafluoroacetone hydrate and hydrogen fluoride can be introduced into the distillation column through separate pipes, or can be mixed and introduced in advance, but the introduction position into the distillation column is preferably the same. The introduction position (height) to the distillation column may be any position from the bottom to the top, but preferably from the theoretical amount of water and hydrogen fluoride produced by the dehydration reaction of HFA · 3W and hydrogen fluoride. It is preferable to introduce into the position (height) of the distillation column corresponding to the boiling point of the resulting mixed liquid.

  The reason why it can be effectively dehydrated in the method of the present invention is that when hexafluoroacetone trihydrate and 1 equivalent or more of hydrogen fluoride are mixed, the reaction or equilibrium shown by the following formula is established in a short time, and in distillation, It is presumed that an equilibrium state consisting of three components of HFA / HF, hydrogen fluoride, and an azeotropic composition of water and hydrogen fluoride is established.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[Example 1] Batch type production method The material of the dehydrator was hexafluoroacetone, hexafluoroacetone trihydrate, and the part in contact with anhydrous hydrogen fluoride was fluororesin or polyethylene. The distillation pot is a 10 cm diameter x 15 cm high polytetrafluoroethylene container, and the distillation tower is filled with polyethylene Raschig rings (4 mm diameter x 4 mm length) 35 cm long as a filler. As a column and a cooler, a PFA made cylinder with a diameter of 10 cm × 15 cm and provided with a serpentine tube through which a refrigerant flows is used, and a 500 ml PFA container is used as a receiver for the effluent from the top. .

  After adding 220 g of HFA · 3W to the distillation pot, it was cooled in a dry ice / acetone bath and solidified. Next, 240 g of hydrogen fluoride was weighed and charged, and set in a distillation column in a cooled state (−20 ° C.). The mixture was allowed to stand to room temperature, and heating was started from the outside with a water bath and an oil bath. During this time, no noticeable exotherm in the distillation pot due to mixing was observed.

  As the heating was continued, reflux was observed at the upper part of the distillation column, and then the temperature of the reflux part began to fall below the boiling point of hydrogen fluoride (19.5 ° C.), confirming the reflux of HFA / HF. At this time, extraction of the reflux liquid was started while ensuring reflux so that the temperature at the top of the column was kept at the boiling point of hydrogen fluoride near 19.5 ° C. The extracted reflux liquid (HFA · nHF) was received in an ice-cooled receiver, and the volume was recorded over time. When an appropriate capacity was accumulated, the container was replaced, the capacity and mass were measured, put into a polyethylene storage container, sealed, and stored in a freezer.

  The temperature of the oil bath was adjusted so that a temperature difference of 20 ° C. or more always occurred because the tower bottom temperature increased with a decrease in the hydrogen fluoride concentration at the bottom of the tower due to the progress of distillation. The temperature at the bottom of the column sometimes showed the temperature of the gas phase part of the distillation pot due to the decrease in the internal volume (the same applies hereinafter). The temperature at the bottom of the column and the distillation column gradually increased, but the temperature at the top of the column was kept almost constant at 20 ° C. so as to maintain a moderate reflux. The distillation was stopped when the column bottom temperature showed 60 ° C.

  After the distillation, the reflux liquid recovered from the top of the column (column top distillate) was 252 g (HFA / nHF molar ratio n4.3, hexafluoroacetone yield 99%), and the bottom liquid was 188 g of fluorine. It was a hydrogen fluoride aqueous solution (71 mass%). When the water content of the reflux liquid was measured by the Karl Fischer method, the presence of water was not confirmed. Hexafluoroacetone was not detected in the bottom liquid.

[Example 2] Batch type production method (a) After completion of distillation in Example 1, 181 g of an aqueous hydrogen fluoride solution (71% by mass) recovered from the bottom of the column, 220 g of HFA · 3W, and 344 g of anhydrous hydrogen fluoride were distilled. It poured into the pot and the distillation similar to Example 1 was started. Distillation was continued while removing the reflux solution at the top of the tower until the bottom temperature showed 51 ° C., and 249 g of the top distillate was obtained (molar ratio of HFA · nHF n4.15, yield of hexafluoroacetone 99%). The column bottom liquid was 489 g of an aqueous hydrogen fluoride solution (76% by mass). When the water content of the top distillate was measured by the Karl Fischer method, the presence of water was not confirmed. Hexafluoroacetone was not detected in the bottom liquid.
(B) After completion of the distillation in (a), 412 g of an aqueous hydrogen fluoride solution (76% by mass) recovered from the bottom of the column was added to the distillation pot, and the same distillation as in Example 1 was started. Distillation was continued while the reflux liquid at the top of the tower was withdrawn until the bottom temperature showed 85 ° C., the top distillate was 197 g of hydrogen fluoride, and the bottom liquid was 275 g of hydrogen fluoride aqueous solution (62 mass). %)Met. When the water content of the top distillate was measured by the Karl Fischer method, the presence of water was not confirmed. Hexafluoroacetone was not detected in the bottom liquid.
(C) After completion of the distillation in (b), 267 g of an aqueous hydrogen fluoride solution (62% by mass) recovered from the bottom of the column was added to the distillation pot, and the same distillation as in Example 1 was started. Distillation was continued while extracting the reflux liquid at the top of the tower until the bottom temperature showed 116 ° C., and the top distillate was 54 g of hydrogen fluoride, and the bottom liquid was 206 g of hydrogen fluoride aqueous solution (48 mass). %)Met. When the water content of the top distillate was measured by the Karl Fischer method, the presence of water was not confirmed. Hexafluoroacetone was not detected in the bottom liquid.

[Example 3] Batch production method Distillation was carried out using the same apparatus as in Example 1. After putting 220 g of HFA · 3 W into the distillation pot, it was cooled in a dry ice / acetone bath. Next, 122 g of hydrogen fluoride was weighed and charged, and set in a distillation column in a cooled state (−20 ° C.). Thereafter, distillation was continued and stopped until the bottom temperature of the column showed 121 ° C. as in Example 1.

  After the distillation, the reflux liquid (column top distillate) recovered from the top of the tower was 229 g (HFA / nHF molar ratio n3.5, hexafluoroacetone yield 99%), and the bottom liquid was 104 g of fluorine. It was a hydrogen fluoride aqueous solution (46 mass%). When the water content of the reflux liquid was measured by the Karl Fischer method, the presence of water was not confirmed. Hexafluoroacetone was not detected in the bottom liquid.

Example 4 Batch Production Method Distillation was carried out using the same apparatus as in Example 1. After putting 220 g of HFA · 3 W into the distillation pot, it was cooled in a dry ice / acetone bath. Next, 271 g of hydrogen fluoride was weighed and charged, and set in a distillation column in a cooled state (−20 ° C.). Thereafter, the distillation was continued and stopped until the column bottom temperature showed 128 ° C. as in Example 1.

  After the distillation, the reflux liquid recovered from the top of the column (column top distillate) was 389 g (molar ratio n11 of HFA · nHF, 99% yield of hexafluoroacetone), and the bottom liquid was 96 g of hydrogen fluoride. It was an aqueous solution (38 mass%). When the water content of the reflux liquid was measured by the Karl Fischer method, the presence of water was not confirmed. Hexafluoroacetone was not detected in the bottom liquid.

[Example 5] Continuous production method The dehydration apparatus is the same as the apparatus shown in Example 1 except that a metering pump (EH-B10SH-100PR9 manufactured by Iwaki Co., Ltd.) is used as the HFA-3W supply device and stainless steel is used as the hydrogen fluoride supply device A cylinder with a needle valve was added to a cylinder equipped with an internal intubation tube and a branch tube. The flow rate was adjusted by the display on the pan scale.

  First, 303 g of a 60% by mass hydrogen fluoride aqueous solution prepared by mixing hydrogen fluoride and water was put into a distillation pot, and distillation was started. When the reflux of hydrogen fluoride was confirmed, 638 g of a mixed solution of HFA · 3W and hydrogen fluoride (molar ratio of hydrogen fluoride to HFA · 3W of 13) was ¼ of the column height from the top of the column. The effluent from the top of the column was collected in a receiver. During the supply of the mixed liquid, the column top temperature was maintained at 16.5 ° C. to 20.5 ° C. by adjusting the distillation amount while maintaining the column bottom temperature at about 107 ° C.

  567 g of the overhead distillate recovered from the top of the tower at the end of the dehydration treatment had a hexafluoroacetone / hydrogen fluoride molar ratio of 10. When the moisture contained in the distillate from the top of the column was measured by the Karl Fischer method, the presence of moisture was not confirmed. The column bottom liquid at the end of the distillation was 370 g of hydrogen fluoride aqueous solution (48% by mass), and no hexafluoroacetone was detected in the column bottom liquid. The overall recovery rate (material balance) was 99.9% or higher, the recovery rate of hexafluoroacetone was 99.6%, and the recovery rate of hydrogen fluoride was 100%.

  Since the dehydration method of the present invention uses hydrogen fluoride as a dehydrating agent, there is an advantage that almost no waste is generated. In addition, since the obtained anhydride is a hydrogen fluoride adduct of hexafluoroacetone, It is particularly effective when hydrogen fluoride is used as a solvent for the reaction.

Claims (5)

Hexafluoroacetone hydrate and hydrogen fluoride are mixed in advance or separately introduced into the distillation column to obtain a composition containing hexafluoroacetone or hexafluoroacetone hydrogen fluoride adduct and hydrogen fluoride as low-boiling components. A method for dehydrating hexafluoroacetone hydrate comprising obtaining a composition containing water and hydrogen fluoride as high-boiling components. The dehydration method according to claim 1, wherein hexafluoroacetone hydrate and hydrogen fluoride are mixed in advance or separately and continuously introduced into the distillation column. Hexafluoroacetone hydrate and hydrogen fluoride are premixed or separately introduced continuously into the distillation column, and the composition contains hexafluoroacetone or hexafluoroacetone hydrogen fluoride adduct and hydrogen fluoride as low-boiling components. A method of dehydrating hexafluoroacetone hydrate comprising continuously obtaining a product from the top of the column and continuously obtaining a composition containing water and hydrogen fluoride as high-boiling components from the bottom of the column. The dehydration method according to claim 1, wherein the hexafluoroacetone hydrate is hexafluoroacetone trihydrate. The dehydration method according to claim 1, wherein the hexafluoroacetone hydrate is hexafluoroacetone hydrate containing water.